A61K 31/70, C07H 17/08
The invention relates to novel 15-membered 8a- and 9a-lactams from the class of the macrolide antibiotic 6-O-methyl-erythromycin A, to intermediates for their preparation, to a process for their preparation, to their pharmaceutically acceptable addition salts with inorganic and organic acids, to their hydrates, to a process for the preparation of pharmaceutical compositions as well as to the use of pharmaceutical compositions for treatment of bacterial infections.
Erythromycin A is a macrolide antibiotic, whose structure is characterized by a 14-membered lactone ring with C-9 ketone and two sugars, L-cladinose and D-desosamine, glycosidically bound in C-3 and C-5 positions onto an aglycone moiety of the molecule (McGuire, Antibiot. Chemother. 1952; 2:281). By an oximation of C-9 ketone with hydroxylamine hydrochloride, by Beckmann rearrangement of the obtained 9(E)-oxime and by a reduction of the formed 6,9-imino ether there is obtained 9-deoxo-9a-aza-9a-homoerythromycin A, the first semisynthetic macrolide with a 15-membered azalactone ring (Kobrehel G. et al., U.S. Pat. No. 4,328,334, 5/1982). By means of a reductive methylation of 9a-amino group, azithromycin, a prototype of a novel class of 9a-azalide antibiotics was synthesized (Kobrehel G. et al., BE 892 357, 7/1982). In addition to having a broad antimicrobial spectrum including also Gram-negative bacteria, azithromycin is also characterized by a long biological half-life, a specific transport mechanism to the site of use and a short therapy time. Azithromycin easily penetrates and accumulates inside human fagocyte cells resulting in improved activity on intracellular pathogenic microorganisms, from classes Legionella, Chlamydia and Helicobacter.
It is known as well that by a O-methylation of C-6 hydroxyl group clarithromycin (6-O-methyl-erhytromycin A) is obtained (Morimoto S. et al., J. Antibiotics 1984. 37. 187). In relation to erythromycin A, clarithromycin is much more stable in acidic medium and exhibits improved in vitro activity against Gram-positive bacterial strains (Kirst H. A. et al., Antimicrobial Agents and Chemother., 1989, 1419).
By recent research on 14-membered macrolides, a novel type of macrolide antibiotics. ketolides, has been discovered, whose structure is characterized by a 3-keto croup instead of a neutral sugar, L-cladinose (Agouridas C. et al., EP 596802 A1 5/1994; Le Martret O., FR 2697524 A1 5/94). Ketolides exhibit significantly improved in vitro activity against MLS (macrolide, lincosamide and streptogramin B) induced-resistant organisms (Jamjian C., Antimicrob. Agents Chemother., 1997, 41, 485).
It has been described as well that by Beckmann rearrangement of 6-O-methyl-erythromycin A 9(E)- and 9(Z)-oximes, hydrolysis of cladinose of the obtained 8a- and 9a-lactams, protection of 2xe2x80x2-hydroxyl group of desosamine, an acylation reaction, an oxidation of 3-hydroxyl group and by deprotection, there are obtained 15-membered 8a- and 9a-ketolides from the class of 6-O-methyl-erythromycin A (Lazarevski G. et al., PCT/HR 99/00004, 4/99).
According to known and established prior art, novel 15-membered 8a- and 9a-lactams from the class of 6-O-methyl-erythromycin A, which are the object of the present invention, their pharmaceutically acceptable addition salts with organic or inorganic acids, their hydrates, methods and intermediates for their preparation and methods for their preparation and use as pharmaceutical preparations have hitherto not been described. The object of this invention is preparation of 11,12-substituted derivatives of 6-O-methyl-erythromycin A 8a- and 9a-lactams and their 3-hydroxy and 3-keto derivatives. A further object of the present invention are 3-acyl derivatives of 6-O-methyl-erythromycin A 8a- and 9a-lactams and 3-acyl-derivatives of 11,12-substituted 6-O-methyl-erythromycin A 8a- and 9a-lactams. Novel 15-membered 8a- and 9a-lactams of the present invention are potential antibiotics for the treatment of Gram-positive and Gram-negative susceptible resistant strains.
Novel 15-membered 8a- and 9a-lactams from the class of 6-O-methyl-erythromycin A of the general formula (I) 
their pharmaceutically acceptable addition salts with inorganic or organic acids and their hydrates, wherein
A stands for NH group and B simultaneously stands for Cxe2x95x90O group, or
A stands for Cxe2x95x90O group and B simultaneously stands for NH group,
R1 stands for OH group, L-cladinosyl group of formula (II) 
or R1 stands for a group of formula (III), 
xe2x80x83wherein
Y stands for hydrogen, C1-C6 alkyl, C1-C6 alkyl group with at least one incorporated O, N or S atom or Y stands for (CH2)nxe2x80x94Ar, wherein (CH2)n stands for alkyl and n stands for 1-10, with or without incorporated O, N or S atoms, and Ar stands for 5-10-membered monocyclic or bicyclic aromatic ring containing 0-3 O, N or S atoms, which is unsubstituted or substituted with 1-3 groups representing halogen, OH, OMe, NO2, NH2, amino-C1-C3 alkyl, amino-C1-C3 dialkyl, CN, SO2NH2, C1-C3 alkyl, or
R1 together with R2 stands for ketone,
R2 stands for hydrogen or together with R1 stands for ketone,
R3 stands for hydrogen or C1-C4 alkanoyl group,
R4 stands for hydrogen or together with R5 stands for ketone,
R5 stands for OH, NH2, amino-C1-C3 alkyl or amino-C1-C3 dialkyl, O(CH2)nAr or S(CH2)nAr, wherein (CH2)n and Ar have the above meanings, or together with R4 stands for ketone,
R6 stands for hydrogen, C1-C6 alkyl, C1-C6 alkyl group with at least one incorporated O, N or S atom, or (CH2)nxe2x80x94Ar group, wherein (CH2)n and Ar have the above meanings, or
R5 and R6 together with intervening atoms form an additional ring of formula (IV) 
xe2x80x83wherein
Z stands for CH2, Cxe2x95x90O, C(NH), SO, SO2, CH2CO, COCH2, CH2CH2CO. COCH2CH2 or CH2CH2, and
X stands for hydrogen, C1-C3 alkyl, NH2, amino-C1-C3 alkyl or amino-C1-C3 dialkyl or (CH2)nxe2x80x94Ar group, wherein (CH2)n and Ar have the above meanings,
are obtained as follows:
Step 1:
The first step of the invention includes a reaction of 6-O-methyl-9a-aza-9a-homo-erythromycin A or 6-O-methyl-8a-aza-8a-homoerythromycin A, obtained according to PCT/HR 99/00004, 4/99, with ethylene carbonate in the presence of inorganic or organic bases, preferably potassium carbonate, in a reaction-inert solvent, preferably in ethyl acetate, yielding corresponding 11,12-cyclic carbonates of the general formula (I), wherein A stands for NH and B simultaneously stands for Cxe2x95x90O group, or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R1 stands for L-cladinosyl group of formula (II) and R2, R3 and R4 are mutually the same and stand for hydrogen, R5 and R6 together with intervening atoms form an additional ring of formula (IVb), wherein Z stands for Cxe2x95x90O group.
Step 2:
11,12-cyclic carbonates obtained in the Step 1, are subjected to hydrolysis with strong acids, preferably with 0.25-1.5 N hydrochloric acid, in a mixture of water and lower alcohols, preferably methanol, ethanol or isopropanol, over 10-30 hours at room temperature, yielding 3-decladinosyl derivatives of general formula (I), wherein A stands for NH group and B simultaneously stands for Cxe2x95x90O group, or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R1 stands for OH group, R2, R3 and R4 are mutually the same and stand for hydrogen, and R5 and R6 together with intervening atoms form an additional ring of formula (IVb), wherein Z stands for Cxe2x95x90O group.
Step 3:
3-Decladinosyl derivatives from the Step 2 are subjected to a selective acylation of the hydroxyl group in 2xe2x80x2-position. Acylation is carried out with chlorides or anhydrides of carboxylic acids with up to 4 carbon atoms, preferably with acetic acid anhydride, in the presence of inorganic or organic bases, in a reaction-inert solvent at a temperature from 0-30xc2x0 C., yielding 2xe2x80x2-O-acyl derivatives of the general formula (I), wherein A stands for NH group and B simultaneously stands for Cxe2x95x90O group, or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R1 stands for OH group, R2 and R4 are mutually the same and stand for hydrogen, R3 stands for acetyl and R5 and R6 together with intervening atoms form an additional ring of formula (IVb), wherein Z stands for Cxe2x95x90O group.
As suitable bases sodium hydrogen carbonate, sodium carbonate, potassium carbonate, triethylamine, pyridine, tributylamine, preferably sodium hydrogen carbonate are used. As a suitable inert solvent methylene chloride, dichloroethane, acetone, pyridine, ethyl acetate, tetrahydrofuran, preferably methylene chloride is used.
Step 4:
2xe2x80x2-Acetyl derivatives from the Step 3 are optionally subjected to a reaction with mixed anhydrides of carboxylic acids of formula Yxe2x80x94COOxe2x80x94R1, wherein Y stands for hydrogen, C1-C6 alkyl, C1-C6 alkyl group with at least one incorporated O, N or S atom, or Y stands for (CH2)nxe2x80x94Ar, wherein (CH2)n stands for alkyl and n is 1-10, without or with incorporated O, N or S atoms, and Ar stands for 5-10-membered monocyclic or bicyclic aromatic ring comprising 0-3 O, N or S atoms, which is unsubstituted or substituted with 1-3 groups representing halogen, OH, OMe, NO2, NH2, amino-C1-C3 alkyl or amino-C1-C3 dialkyl, CN, SO2NH2, C1-C3 alkyl and R1 is a group which is usually used for the preparation of mixed anhydrides such as pivaloyl, p-toluenesulfonyl, isobutoxycarbonyl, ethoxycarbonyl or isopropoxycarbonyl group, in the presence of inorganic or organic bases, in a reaction-inert solvent, preferably in methylene chloride, at a temperature from 0-30xc2x0 C. for 3-100 hours, yielding 3-acyl derivatives of general formula (I), wherein R1 stands for a group of formula (III), wherein Y has the above meanings, A stands for NH group and B simultaneously stands for Cxe2x95x90O group, or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R2 and R4 are mutually the same and stand for hydrogen. R3 stands for acetyl and R5 and R6 together with intervening atoms form an additional ring of formula (IVb), wherein Z stands for Cxe2x95x90O group, which are subsequently subjected to deprotection with lower alcohols, preferably in methanol, at a temperature from room temperature to the reflux temperature of the solvent, yielding a compound of the general formula (I), wherein R3 stands for hydrogen and all remaining substituents have the above meanings.
Step 5:
2xe2x80x2-Acetyl derivatives from the Step 3 are optionally subjected to oxidation of the hydroxyl group in C-3 position of an aglycone ring according to a modified Moffat-Pfitzner process with N,N-dimethyl aminopropyl-3-ethyl-carbodiimide in the presence of dimethyl sulfoxide and pyridinium trifluoroacetate as a catalyst in an inert organic solvent, preferably in methylene chloride, at a temperature from 10xc2x0 C. to room temperature, yielding 3-oxo derivatives of the general formula (I), wherein A stands for NH group and B simultaneously stands for Cxe2x95x90O group, or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R1 together with R2 stands for ketone, R3 stands for acetyl, R4 stands for hydrogen and R5 and R6 together with intervening atoms form an additional ring of formula (IVb), wherein Z stands for Cxe2x95x90O group, which are subsequently subjected to deprotection in lower alcohols, preferably in methanol, at a temperature from room temperature to the reflux temperature of the solvent, yielding a compound of the general formula (I), wherein R3 stands for hydrogen and all remaining substituents have the above meanings.
Step 6:
By subjecting 6-O-methyl-9a-aza-9a-homoerythromycin A or 6-O-methyl-8a-aza-8a-homoerythromycin A obtained according to PCT/HR 99/00004, 4/99, to hydrolysis with strong acids as described in the Step 2, followed by a selective acylation of 2xe2x80x2-position as in the Step 3 and by a reaction with mixed anhydrides as in the Step 4, there are obtained compounds of the general formula (I), wherein R1 has the meaning of a group of the formula (III), wherein Y stands for hydrogen, C1-C6 alkyl, C1-C6 alkyl group with at least one incorporated O, N or S atom, or Y stands for (CH2)nxe2x80x94Ar, wherein (CH2)n stands for alkyl and n stands for 1-10, without or with incorporated O, N or S atoms, and Ar stands for 5-10-membered monocyclic or bicyclic aromatic ring containing 0-3 O, N or S atoms, which is unsubstituted or substituted with 1-3 groups representing halogen, OH, OMe, NO2, NH2, amino-C1-C3-alkyl or amino-C1-C3 dialkyl, CN, SO2NH2, C1-C3 alkyl, R2, R3, R4, and R6 are mutually the same and stand for hydrogen and R5 is OH group.
Step 7:
By subjecting 6-O-methyl-9a-aza-9a-homoerythromycin A or 6-O-methyl-8a-aza-8a-homoerythromycin A obtained according to PCT/HR 99/00004, 4/99, to hydrolysis with strong acids as described in the Step 2, followed by a selective acylation of 2xe2x80x2-position as in the Step 3 and by oxidation and deprotection as in the Step 5, after purification with low pressure chromatography on a silica gel column using the system ethyl acetate-(n-hexane)-diethyl amine 10:10:2 and by subsequent evaporation of chromatographically homogeneous fractions with lower Rf and rechromatography in the system CH2Cl2xe2x80x94CH3OH-conc.NH4OH 90:9:0.5, there is obtained a compound of the general formula (I), wherein A stands for NH group and B simultaneously stands for Cxe2x95x90O group or A stands for Cxe2x95x90O group and B simultaneously stands for NH group, R1 together with R2 stands for a ketone, R3 and R6 are mutually the same and stand for hydrogen and R4 together with R5 stands for a ketone.
Alternatively, compounds from the Step 4 can be obtained by subjecting the compounds from the Step 6 to a reaction with ethylene carbonate in a manner as described in the Step 1.
Alternatively, the compounds from the Step 2 can be obtained by changing the sequence of the reaction steps in such a manner that 6-O-methyl-9a-aza-9a-homoerythromycin A or 6-O-methyl-8a-aza-8a-homoerythromycin A obtained according to PCT/HR 99/00004, 4/99, are first subjected to a hydrolysis with strong acids as described in the Step 2 and then to a reaction with ethylene carbonate in a manner described in the Step 1.
Alternatively, the compounds of the Step 5 can be obtained in such a manner that 3-decladinosyl-3-oxo-6-O-methyl-9a-aza-9a-homoerythromycin A or 3-decladinosyl-3-oxo-6-O-methyl-8a-aza-8a-homo-erythromycin A obtained according to PCT/HR 99/00004, 4/99, are subjected to a reaction with ethylene carbonate in the manner described in the Step 1.
Pharmaceutically acceptable addition salts which are also an object of the present invention, are obtained by a reaction of novel compounds from the class of 6-O-methyl-9a-aza-9a-homo- and 6-O-methyl-8a-aza-8a-homo-erythromycins A of the general formula (I), wherein A, B, R1, R2, R3, R4, R5 and R6 have the above meanings, with an at least equimolar amount of a suitable corresponding inorganic or organic acid such as hydrochloric, hydroiodic, sulfuric, phosphoric, acetic, propionic, trifluoroacetic, maleic, citric, stearic, succinic, ethylsuccinic, methanesulfonic, benzenesulfonic, p-toluenesulfonic, laurylsulfonic acid and the like, in a reaction-inert solvent. Addition salts are isolated by filtration if they are insoluble in the reaction-inert solvent, by precipitation by means of a non-solvent or by evaporation of the solvent, most frequently by lyophilization.